Competitions at the Olympic Games are consisted of the Olympic sports. Each Olympic sport is represented by the International Federation (IF), which responsible for the development of this sport. Sport can be represented at the Olympic Games only if the corresponding International Federation is officially recognized by the International Olympic Committee. The decision on the number of sports presented at each Olympic Games is taken by the International Olympic Committee. International Olympic Committee subdivides some Olympic sports into multiple disciplines. This subdivision is quite informal and occurs in cases where disciplines are quite different from each other and are often assumed by people as separate sports, for example swimming and water polo in aquatics. Some sports, known as "discontinued sports", are no longer present on the current program of Olympic Games. Usually summer sports are present in the program of the Summer Olympic Games, and winter sports are present in the program of the Winter Olympic Games. However, figure skating in 1908 and in 1920 and ice hockey in 1920 were present in the program of the Summer Olympic Games.